Credit reporting giant TransUnion has disclosed a data breach affecting more than 4.4 million customers' personal information. In a filing with Maine's attorney general's office on Thursday, TransUnion attributed the July 28 breach to unauthorized access of a third-party application storing its customers' personal data. TransUnion claimed "no credit information was accessed," but provided no immediate evidence for its claim. The data breach notice did not specify what specific types of personal data were stolen.